The invention relates to a screw-type solid bowl centrifuge for centrifuging material that has a tendency to foam.
Centrifuges in the form of screw-type solid bowl centrifuges have been known in various embodiments for a long time. A known centrifuge is illustrated in FIG. 2. When processing easily oxidizing material to be centrifuged, consisting, for example, of cut-up fruit, such as apples it is desirable to minimize as much as possible the possibility of an oxidation of the material to be centrifuged during the centrifugal treatment.
The centrifuge of the present invention addresses this problem and solves it. The centrifuge""s feed section that goes through the feed pipe and the distributor into the centrifuge chamber together are designed as an essentially hermetically closed system, which in a simple manner reduces the possibility of an oxidation of the product to be centrifuged in the feed system or section of the drum. The other sections of the centrifuge may have a closed design. A hydrohermetical feed already reduces the oxidation.
According to an embodiment of the invention, the feed pipe preferably is fixedly connected with a screw by way of a distributor, so that the feed pipe rotates along with the screw during rotations of the screw. In this manner, in contrast to prior the art illustrated in FIG. 2, a xe2x80x9csoftxe2x80x9d preacceleration and thus a correspondingly careful treatment of the material to be centrifuged is achieved. Because the feed pipe has a rotatable design, it is, in addition, possible to connect the distributor and the feed pipe directly in a xe2x80x9cone-piecexe2x80x9d manner with one another without a gap or an opening, so that foam can no longer penetrate into any gaps or spaces between the feed pipe and the distributor, as was the case in the prior art.
The hygienic effect is increased by the further measure of connecting the distributor directly without a gap or an opening in circumferential openings of a screw body. This creates a free path which has no gaps or openings from the feed pipe into the centrifuge chamber of the centrifuge. In contrast to the prior art, material to be centrifuged can no longer reach the area between the outer circumference of the feed pipe and the inner circumference of the screw body because this feed section of the centrifuge is designed in a xe2x80x9chydrohermeticallyxe2x80x9d closed manner.
According to another embodiment of the invention, the distributor has an essentially pipe-shaped construction, so that it has at least onexe2x80x94preferably twoxe2x80x94radial discharge openings leading into the centrifuge chamber. The distributor may have a radial dimension such that, during the operation of the centrifuge, it projects into the liquid or under the liquid level in the centrifuge chamber, so that when its radial discharge openings are situated under the liquid level, the effect of the hermetic closing of the feed section of the centrifuge is further improved. This measure also contributes to see that a particularly careful treatment of the product/material to be centrifuged takes place.
During the processing of material to be centrifuged, in addition to a solid and a liquid phase in the centrifuge, there is a tendency to form a foam as a third phase. The foam comes from, for example, a fruit mash for producing fruit juice or a highly protein-containing material to be centrifuged. The problem arises that, in an undesired manner, the foam also exits the centrifuge through a liquid discharge port and thereby impairs the quality of the liquid phase. In the case of highly foaming products, there is also the problem that the foam contaminates the centrifuge, particularly in that it enters into gaps at the discharge of the feed pipe into the distributor and, in the worst case, virtually wells out of the centrifuge. The present invention also addresses eliminating this problem.
The present invention includes a baffle plate arrangement which is designed for preventing foam, generated during the centrifuging of material, from exiting through the liquid discharge port or through a solids discharge port.
The baffle plate arrangement has at least one or, preferably, two baffle plates which project into the liquid level one of the baffle plates preferably being arranged between the distributor and the liquid discharge port on the screw body, and the other baffle plate being arranged between the distributor and the solids discharge port on the screw body. At least one of the baffle plates projects into the liquid level and thereby forms a barrier in the direction of the corresponding discharge port for foam formed during the centrifuging of the material to be centrifuged.
According to another embodiment of the invention, at least one of the baffle plates is formed directly on the distributor and/or on the outer circumference of the screw body adjacent the distributor.
Furthermore, one of the baffle plates is preferably constructed as a solid-ring baffle without openings, and the other baffle plate is provided with openings toward its inner circumference for the passage of foam in the direction of the solids discharge port. The baffle plate located preferably between the distributor and the solids discharge port is dimensioned such that only a relatively narrow gap exists between the drum and the baffle plate. The narrow gap is designed such that a slimy solid phase can pass through it, in which case a return flow through the narrow gap is prevented by a pushing solid phase which follows.
A particularly advantageous effect is achieved by means of a combination of baffle plates and the rotatable sealed-off feed pipe, because this arrangement meets the highest hygienic requirements with respect to the feeding of material to be centrifuged as well as with respect to the foam barrier in the direction of the liquid discharge port.
Other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings.